Magnetorheological down-hole packing elements

ABSTRACT

Aspects of drilling, production, hydraulic fracturing, and well work-over operations operations that create full seal magnetorheological down-hole packing elements are described. Some examples describe a system that includes a magnetorheological fluid and a magnetic assembly tool (installed on a work-string) configured to generate a magnetic field and create, in a flow of the magnetorheological fluid, a semi-solid packing element, and/or a magneto-rheological effect altering the fluid viscosity, in a drill pipe, casing, or hole. Various examples also include disclosure of methods for releasing stuck pipe, controlling fluid loss while drilling, open-hole packing, conforming, plugging and abandoning, and multistage fracturing that can reduce operational risks and non-productive time.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/626,797 entitled “MAGNETORHEOLOGICAL DOWN-HOLE PACKING ELEMENTS,” filed Feb. 6, 2018, the contents of which being incorporated herein by reference in their entirety.

BACKGROUND

Although little is known by the public in general about magnetorheological fluids (MRFs), MRFs have been adopted at an industrial scale over the last decade. MRFs can have a suspension of magnetic particles in a liquid. Under the influence of a magnetic field, the suspended magnetic particles interact to form a new structure that resists shear deformation or flow. The interaction of these particles and the magnetic field restricts motion of the fluid, therefore, increasing its rheological properties. This feature has attracted scientists and technology companies to use these fluids to overcome old engineering limitations. The relevance of these fluids is such that several applications using MRF are found in dampers, bridges, body armors, and shock absorbers systems, among others.

The properties of MRF depend in part on the magnetizable particles volume fraction (dispersed phase), the carrier fluid (continuous phase), and the strength of the magnetic field. The fluid structure once a magnetic field is applied is accountable for the formation and reversibility from a free-flowing liquid to a semi-solid. The reversibility is of importance and may be tuned for certain applications. On the one hand, soft magnetic materials can be easily magnetized and demagnetized, which provides a better control over the MRF. On the other hand, hard magnetic materials can maintain the magnetized fluid structure in the absence of the presence of the magnetic field. This fact is of importance because depending on the application, an independent design needs to be considered.

Although conventional drilling fluids in the oil and gas industry have been used extensively for several decades, these fluids remain limited to crucial application where MRF can be proven more beneficial. The drilling fluids in the industry are a mixture of a carrier phase, either water or oil, and chemical additives designed to set the properties of this fluid. Two of these properties are viscosity and yield stress, known in fluid mechanics as rheological properties. Setting the rheological properties of a drilling fluid is important because they determine flow behavior in the downhole, the debris removal capacity while drilling, and the expected operational pressures to maintain wellbore stability. A drilling fluid can be a drilling mud, a cementing slurry, a completions fluid, or any other type of fluid used while drilling a well. Although conventional drilling fluids in the oil industry have been used extensively for several decades, the rheological properties of those fluids can in many cases only be set at surface by adding chemical additives and cannot be tuned once these fluids are pumped downhole. This is a natural limitation for these fluids, making any rheological change time consuming, non-immediately reactive, and frequently expensive because of the high amount of volume to be treated with chemicals.

The rheology in MRF drilling fluids, which can be formed by the addition of magnetic particles to conventional drilling fluid, are not chemically dependent. The change of the rheological properties of an MRF can be tuned according the intensity and direction of a magnetic field applied to the fluid. This feature allows any rheological change to be achieved even downhole or at surface when a magnetic field of a certain intensity is applied to the MRF with fixed magnets or electromagnets. Thus, MRFs can be used to develop a rapid and localized rheology modification, which makes the use of magnetorheological drilling fluid less expensive and more efficient than using conventional drilling fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments described herein and the advantages thereof, reference is now made to the following description, in conjunction with the accompanying figures briefly described as follows:

FIGS. 1A-1F illustrate a first example of a full seal magneto-rheological down-hole packing element as a method of releasing stuck pipe according to various example embodiments described herein.

FIGS. 2A-2F illustrate a second example of a full seal magneto-rheological down-hole packing element as a method of releasing stuck pipe according to various example embodiments described herein.

FIGS. 3A-3F illustrate a first example of a full seal magneto-rheological down-hole packing element as a fluid loss controller while drilling according to various example embodiments described herein.

FIGS. 4A-4D illustrate a second example of a full seal magneto-rheological down-hole packing element as fluid loss controllers while drilling according to various example embodiments described herein.

FIGS. 5A-5F illustrate a third example of a full seal magneto-rheological down-hole packing element as fluid loss controllers while drilling according to various example embodiments described herein.

FIGS. 6A-6C illustrate a process of drilling and completion of a well according to various example embodiments described herein.

FIGS. 6D-6H illustrate an example use of MRF for multistage fracturing.

FIGS. 6I-6J illustrate a first and second example of a full seal magneto-rheological packing element as open-hole packers for well completion according to various example embodiments described herein.

FIG. 7 illustrates an example of a full seal magneto-rheological down-hole packing element as a mechanical barrier to isolate unwanted water or gas according to various example embodiments described herein.

FIGS. 8A-8B illustrate an example of a full seal magneto-rheological down-hole packing element to set at a designated depth in a plug and abandonment operation according to various example embodiments described herein

FIGS. 9A-9B illustrate an example of a full seal magneto-rheological down-hole packing element as a selective-resettable zonal packer according to various example embodiments described herein.

FIGS. 10-13 show examples of magnet arrangements according to various example embodiments described herein.

FIGS. 14-16A show examples of magnetic assembly tools for generating magnetic fields according to various example embodiments described herein.

FIG. 16B shows an example of a downhole assembly for transforming kinetic energy into electric energy according to various example embodiments described herein.

FIG. 16C shows a chart of pressure drop vs. amount of weighting material according to various example embodiments described herein.

FIGS. 17-19 show examples of locations for magnet arrangements according to various example embodiments described herein.

FIGS. 20-24 show examples of packing mediums according to various example embodiments described herein.

FIGS. 25 and 26 show examples of packing mechanisms according to various example embodiments described herein.

FIG. 27 illustrates an example of a schematic for an experimental setup according to various example embodiments described herein.

FIG. 28 depicts a Rheogram for MRF CIP wt % 10.5 according to various example embodiments described herein.

FIG. 29 illustrates a chart of an annular pressure drop according to various example embodiments described herein.

FIG. 30 illustrates a chart of a pressure drop in a drill-pipe & annulus according to various example embodiments described herein.

FIG. 31 illustrates a chart of a pressure drop measurement drip-pipe & annulus with MRF CIP wt % 10.5 after 60 hours static according to various example embodiments described herein.

The drawings illustrate only examples and are therefore not to be considered limiting of the scope described herein, as other equally effective examples are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the examples. For example, a very smooth transition with smoothly bent pipe may, for the purpose of better understanding the phenomenon, may be shown in the drawings as a sharp bend right after a vertical section. Additionally, certain dimensions may be exaggerated to help visually convey certain principles. In the drawings, similar reference numerals between figures designate like or corresponding, but not necessarily the same, elements.

DETAILED DESCRIPTION Use of MRF for Releasing Stuck Pipe

Stuck pipe refers in the oil & gas industry to any tool, such as drill pipes, drill collars, stabilizers, motors, reamers, or logging tools, that is stuck in the borehole and make the drill string immobile. Stuck pipe can occur while drilling, tripping, logging, or running casing. There are generally two types of stuck pipe mechanisms, including (1) Differential Sticking and (2) Mechanical Sticking. Differential sticking occurs when there is an overbalance of pressure between the fluid in the wellbore and the formation fluid. When a tool touches the borehole wall of a depleted formation (e.g., a low pressure zone), the pressure exerted by the hydrostatic column above it pushes the pipe against the borehole wall. The differential pressure over the tool creates the differential sticking. A mud cake generated by the drilling mud to provide wellbore stability is squeezed by the stuck pipe, exacerbating the problem. In consequence, the tool remains immobile and rotation or reciprocation is impaired.

When the tool remains at the center of the borehole, the hydrostatic pressure of the mud over the tool is distributed radially and no differential sticking takes place. Some factors affect the probability of differential sticking, such as:

a. The differential pressure between the wellbore exerted by the mud hydrostatic column and the pressure of the formation fluids. The greater the differential pressure, the higher the probability of occurrence.

b. The drilling mud dehydrates against the permeable formations creating a mud cake that provides wellbore stability. If the mud cake is too thick, there is more contact area with the cylindrical tool, increasing the probability of occurrence.

c. If the contact area of the tool is too large, there is an increasing probability of occurrence.

Mechanical sticking on the other hand refers to a tool stuck in a collapsed well, based on the accumulation of solids or debris around the tool. During differential sticking, the well can be circulated. That is, the mud or any treatment can be pumped downhole and recovered at the surface. That provides an advantage compared to mechanical sticking when well circulation can be impaired. In general, the release mechanism during a differential sticking includes:

d. Reduce the mud weight (mud density) to decrease the fluid hydrostatic in the wellbore and hence the pressure differential. This mechanism can be limited when the formation integrity is at risk.

e. Use spotting fluids intended to degrade the mud cake, reducing the contact areas of the formation and the stuck tool.

f. A combination of the previous two mechanisms.

Some problems can be encountered while applying these mechanisms. Reducing the mud weight can make the wellbore susceptible to wellbore instability, leading to wall collapse or formation fluid migration to the wellbore due to an underbalance condition. Additionally, to reduce significantly the hydrostatic over the problematic zone, a long column of light fluid needs to be in the wellbore, changing the pressure profile of the well. Experience has shown that the spotting fluids need a soaking time to effectively degrade the mud cake. This waiting time is non-productive time, and it delays the drilling operations and increases the operational costs.

The MRF can provide a competitive solution to overcome this problematic. When MRF is activated in the annulus, it can form an open-hole packer that withstands the hydrostatic pressure above it. The pressure below the packer can be modified (e.g., reduced) locally to decrease the differential pressure over the stuck pipe to a point that the formation fluids pressure can help to release the pipe.

In view of the stuck pipe problem and limitations on the conventional techniques used to address it, one example described herein uses a tool with permanent magnets with a coil tubing set or wireline to set a packer to release a differential sticking. Another example is to use a bottom hole assembly (BHA) with permanent magnets preinstalled to set a packer to release a differential sticking.

FIGS. 1A-1F illustrate a first example of a full seal magneto-rheological down-hole packing element as a method of releasing stuck pipe according to various example embodiments described herein. In this example, permanent magnets can be run with coiled tubing and an injection of nitrogen at the bottom to release the stuck pipe condition as described below.

To illustrate the concept, FIG. 1A shows a differential sticking due to a wellbore pressure being larger than a formation pressure. FIG. 1A depicts a first hydrostatic pressure of a subnormal pressurized formation being much less than a second hydrostatic pressure of a borehole. In the example, drilling through the subnormal pressurized formation leads to the differential sticking. This condition results in the pipe being pushed against the borehole wall, and can also lead to the generation of a thick mud cake surrounding the area where the pipe is pushed against the borehole wall. The bend of the pipe is representative and exaggerated in FIG. 1A, and the manner in which a pipe is pushed against the borehole wall can occur in other ways.

According to the methods described herein, FIG. 1B shows running a coiled tubing having permanent magnets positioned at the end of the coiled tubing to a location above the stuck pipe. The coiled tubing can be positioned at the location above the stuck pipe in any suitable way. FIG. 1C shows pumping MRF through the coiled tubing. The MRF can flow through the remaining length of the drill pipe, exit through the end of the drill pipe and/or drilling head, and return up through the annulus. When the MRF reaches a region close to where the permanent magnets are positioned, the MRF can be activated. The process causes the MRF to solidify in front of the magnets to form an open-hole packer. The open-hole packer can withstand the hydrostatic pressure above it. A first hydrostatic pressure P1 represents a pressure that is much less than a third hydrostatic pressure P2′ below the open-hole packer.

FIG. 1D shows pumping nitrogen through the coiled tubing so that the nitrogen enters the annulus. The MRF packer with pumping of nitrogen allows modifying (reducing) the pressure locally to decrease the differential pressure over the stuck pipe to a point that the formation fluids pressure can help to release the pipe. By way of example, a first hydrostatic pressure P1 represents a pressure that is less than a third hydrostatic pressure P2′ below the open-hole packer.

FIG. 1E shows reducing the mud weight by the injected nitrogen. The nitrogen expands in the annulus while travelling up, decreasing the hydrostatic column. In this example, pumping nitrogen from the surface and activating the MRF packer allows reducing the mud weight.

FIG. 1F shows a first hydrostatic pressure P1 representing a pressure that is greater than a third hydrostatic pressure P2′ below the open-hole packer. Once the formation pressure is higher than the wellbore pressure, the formation pressure pushes the pipe back toward the center of the wellbore, releasing it. In this way, FIGS. 1A-1F demonstrate a first example of a full seal magneto-rheological down-hole packing element as a method of releasing stuck pipe according to various examples described herein.

FIGS. 2A-2F illustrates a modified version of the first example. In this example, permanent magnets have been preinstalled at a position on a bottom hole assembly (BHA). FIG. 2A shows that a differential sticking occurs due to a wellbore pressure being larger than a formation pressure. At this point, FIG. 2A depicts a first hydrostatic pressure P1 being much less than a second hydrostatic pressure P2 of a borehole, pushing a pipe against the borehole wall.

FIG. 2B shows pumping the MRF liquid ahead of nitrogen. This scenario includes arranging permanent magnets on the BHA, as depicted. FIG. 2C shows pumping nitrogen after the MRF through the drill string. The figure depicts locating the MRF liquid below the magnet arrangement of magnets and into the region of the borehole near the sub-normal pressurized formation. A first hydrostatic pressure P1 represents a pressure that is much less than a third hydrostatic pressure P2′ below the arrangement of magnets.

FIG. 2D shows the MRF and the nitrogen entering the annulus. The nitrogen reduces the mud weight. A first hydrostatic pressure P1 represents a pressure that is much less than a third hydrostatic pressure P2′ below the arrangement of magnets. FIG. 2E shows activating the MRF semi-solid by the permanent magnets, creating a sealing mechanism. This figure depicts a third hydrostatic pressure P2′ that is equal to a second hydrostatic pressure P2. Additionally, a first hydrostatic pressure P1 is shown as greater than the third hydrostatic pressure P2′. The third hydrostatic pressure is now representative of a hydrostatic pressure below the MRF packer.

FIG. 2F shows waiting for when the second hydrostatic pressure, represented in this case by a P2′, is decreased as compared to P2. The decrease is due to gas migration and gas expansion. Once the formation pressure is higher than the wellbore pressure, the formation pressure pushes the pipe back toward the center of the wellbore, releasing the differential sticking.

In this way, FIGS. 2A-2F demonstrate a second example of a full seal magneto-rheological down-hole packing element as a method of releasing stuck pipe according to various examples described herein. The MRF packer may be capable of withstanding a considerable amount of hydrostatic pressure. Thus, the pressure below the packer can be reduced and a releasing operation can take place. This method presents a relatively cheap and fast way to reduce the pressure below the MRF packer, by pumping a lighter fluid such as nitrogen, water, or a lighter mud with a coiled tubing.

The current technology for releasing a stuck pipe, called BLACK MAGIC™ spotting fluid, needs a soaking time. Sometimes several cycles of BLACK MAGIC™ spotting fluid are pumped to release the stuck pipe. If there is a differential sticking where circulation is allowed, an MRF spotting fluid can be pumped and located downhole in proximity to permanent magnets as described above. This can create a packing effect that would reduce the hydrostatic over the pipe, generating a potential reduction of the hydrostatic. If that occurs in effect, there is a potential to release the stuck pipe.

Use of MRF as a Fluid Loss Controller while Drilling

A fluid loss occurs when the drilling fluid migrates to subsurface thief formations. Frequently, these formations are characterized for being highly permeable or naturally fractured. In consequence, the drilling fluid that is supposed to be circulating from surface to downhole, and from downhole to surface, is lost in these formations and cannot be recovered, as shown between FIGS. 3A and 3B. The lost volume needs to be compensated by mixing more fluid, but drilling fluids are expensive. Therefore, fluid loss is undesirable and should be prevented or mitigated.

By using conventional drilling fluids, one mitigation alternative is adding high size solids, also known as bridging agents or lost-circulation materials (LCMs). Although LCMs have been extensively used, using high size solids can damage the producing formation and reduce the oil or gas productivity in the long run. Additionally, the concentration and particle size should be limited to avoid damaging the expensive BHA, particularly the motor and measurement-while-drilling (MWD) components.

MRF can be used to thicken the drilling fluid and avoid fluid loss because they are capable of building a pressure and flow-prevention seal. Doing that, fluid loss mitigation can be immediate, localized, and may not affect the well productivity. Once the treatment fluid is located at the thief zone, a magnetic field can be applied to the fluid by using fixed magnets attached to the pipe. The increased viscosity and yield stress of the fluid will avoid the treating fluid to flow towards the thief zones. The treating fluid can be mixed with some cementitious material to set with time and seal the thief zones even when no magnetic field is applied.

More research may determine whether strong magnetizable particles (e.g., CIP) can maintain their structure even when no magnetic field is applied. Although the principle works theoretically, current experimentation is being performed to determine how the magnets need to be placed in the pipe to generate the intensity and direction of the magnetic waves desired. This aspect is relevant because the treating fluid is pumped downhole and, once located at the thief zone, the pipe is retrieved to allow the fluid to set, avoid the consequence of any stuck pipe. In some cases, the magnetorheological effect can be lost if the pipe is retrieved with the magnets. One feasible workaround would be to look for magnetic particles that sustain a magnetorheological effect even when no magnetic field is applied to them. Thus, the use of MRF can be proven to be beneficial to solve fluid loss, a very common problematic while drilling a well.

To illustrate the concept, FIGS. 3A-3B illustrate drilling operations in an ideal and in a fluid loss scenario, respectively. As shown in FIG. 3A, a drilling operation in an ideal scenario has an example fluid phenomena associated with a normal pressurized formation. A drill string is typically made up of three or more sections, including a BHA, a transition pipe, and a length of drill pipe. Generally, the drill string is hollow, and drilling fluid is pumped down through the drill string and circulated back up a void (i.e., the annulus) between the drill string and the wellbore and/or casing. Drilling fluid can be pumped down through the drill string using pumps, and torque can be provided to the drill bit using a kelly or top drive, for example, among other types of known drive mechanisms. In an ideal scenario, drilling fluid is circulating from surface to downhole, and from downhole to surface.

FIGS. 3C-3D illustrate an example of curing fluid losses on the fly using an arrangement of permanent magnets on the BHA and a hard grade CIP. There are advantages to curing fluid losses while drilling. To reduce operational risks and non-productive time (NPT), drilling operations should not stop. In that sense, MRF presents a competitive advantage if used to cure fluid losses on the fly, i.e., through the mitigation of fluid losses while drilling operations can continue. In that sense, an MRF with hard magnetizable particles can be used to maintain the chain-like structure in the absence of the presence of the permanent magnet placed on the BHA.

The process includes adding hard grade CIP to the circulating mud. The mixture travels through the BHA as a fluid phase. Once the mixture enters the annulus at a slow flow rate, its rheological properties are modified by the presence of the permanent magnets on the BHA. It is expected that the rheology development creates a semi-solid that blocks the thief zones. The activated MRF blocks the thief zones near the wellbore and beyond. The annulus can be momentarily blocked by the activated MRF. When the circulation of drill fluid is re-established, the increase in the flow rate can create enough shear to brake the MRF chain in the annulus while the thief zone is still isolated. The drilling process can be resumed and more CIP particles added, to the extent necessary, in some examples.

The MRF can be used to thicken the drilling fluid and avoid fluid loss because it is capable of building a pressure and flow-prevention seal. Doing that, the fluid loss mitigation can be immediate, and localization can be done in a way that will not affect well productivity. Once the treatment fluid is located at the thief zone, a magnetic field can be applied to the fluid by using fixed magnets attached to the pipe or the BHA. The increased viscosity and yield stress of the fluid will avoid the treating fluid to flow towards the thief zones. In some cases, the treating fluid can be mixed with some cementitious material to set with time and seal the thief zones even when no magnetic field is applied.

FIG. 3C shows some fluid is being lost in a drilling operation. FIG. 3D shows pumping in the MRF fluid treatment. The MRF fluid treatment in this example includes mixing hard grade CIP with MRF. This procedure can also include preinstalling magnets on the BHA before the trip-in, or using a BHA that has magnets preinstalled. FIG. 3E shows activating the MRF through proximity and/or contact with the magnets. The activated MRF travels is a gelled or solidified state towards the thief zone. The activation can be accomplished by causing the permanent magnets arranged as part of the BHA to generate a magnetic field.

FIG. 3F shows drilling out the cement and re-establishing the circulation in the annulus at higher flow rates. As such FIGS. 3C-3F illustrate a first example of a full seal magnetorheological down-hole packing element as a fluid loss controller while drilling according to various examples described herein.

Use of MRF to Avoid Fluid Losses with Cement Slurry and Balanced Plug Technique

When fluid losses are severe and the BHA needs to be pulled out of the hole, MRF can provide an advantageous alternative to overcome problem. In severe cases, the cement slurry itself is not capable to cure fluid losses because of its fluid nature. The cement slurry, in that sense, will continue flowing through the thief zone until the setting time is reached, generally 2-3 hours, leaving the near wellbore zone exposed to additional thief zones and more fluid losses. When MR cement slurry is used, the gelling or semisolid effect can be created immediately near the wellbore. A balanced plug technique for placing the MR cement slurry can be useful so that a longer stinger with a magnet arrangement can be used to activate the fluid. After the fluid is balanced and the stinger pulled out, the magnets are left in contact with the fluid and activate it near the wellbore. A polycrystalline diamond compact (PDC) bit can be used to drill-out the cement and the tool that has the magnets.

FIGS. 4A-4D illustrate an example of this type. The process can rely upon an apparatus that includes a an arrangements of magnets. FIG. 4A shows balancing (spotting) a cement slurry at the problematic zone. The slurry is pumped down the pipe and exits through holes at the end of the pipe. FIG. 4A also shows placing the arrangement of magnets below the cement slurry and waiting for the fluid to migrate to the thief zone. FIG. 4B shows withdrawing the pipe to some extent and, thus, placing the arrangement of magnets in proximity and/or contact with the MRF.

FIG. 4C shows an example of keeping the magnets in contact with the MRF to create the semi-solid effect. Initially, this can include pulling the pipe out of the hole to complete the activation. Finally, FIG. 4D shows drilling out the cement and magnets. The magnets can be recovered in some cases at the surface. In this way, shown is a second example of a full seal magneto-rheological down-hole packing element as fluid loss controller while drilling according to various examples described herein.

In the example shown in FIGS. 5A-5F, fluid losses are controlled using a balanced plug and hard grade CIP. The hard grade CIP is also known as hard grade magnetizable particles. This approach can include placing a cylindrical magnet at the bottom of the pipe. The cylindrical magnet can activate the MR cement slurry as the pipe is pulled out of the hole. In this example, the magnets and pipe can be immediately recovered.

FIG. 5A shows balancing (spotting) a cement slurry in front of the problematic zone. In this example, the process includes using permanent magnets that can be arranged as part of the BHA. FIG. 5B shows placing the arrangement of magnets in proximity and/or contact with the MRF. At this point, the process includes causing the permanent magnets to apply a magnetic field to the semi-solid MRF and cementitious material. Contacting the MRF with the magnets, and waiting for the fluid to migrate to the thief zone, creates a semi-solid or gelling effect.

FIG. 5C shows pulling the pipe out of the hole to complete the activation. FIG. 5D shows the semisolid MRF remains active in the thief zone while the cements solidifies. FIG. 5E shows blocking the thief zone with the cement. FIG. 5F shows drilling out the cement and resuming drilling.

Introduction to Well Completions

Once a well is drilled to the target formation and a formation evaluation has taken place, the well can become a producer or can be abandoned. Well completions refer to the series of steps followed to convert a drilled hole into a producer. Therefore, some decisions must be considered to optimize the productivity and the costs of the well. Principally, there are three types of completions, including (1) Barefoot, (2) Open Hole, and (3) Cased Hole. In a barefoot completion, no tubulars are run into the well. This type requires a very strong and competent formation.

In open hole completions, a steel pipe (casing) is run into the drilled well to protect the interest zones. However, the casing or liner is not cemented. The cased hole can be cemented when a better formation stability and formation selectivity is desired. Horizontal open hole completions have become common today because that extends the contact of the interest zone with the wellbore, maximizing the well productivity. Open hole completions are accompanied by open-hole packers, such as mechanical packers or swelling elastomers to provide zonal isolation.

In extended horizontal wells, interval segmentation takes place to control the heterogeneities of the formations. Some reservoirs can exhibit different permeability contrasts. In such cases, open hole packers are used to provide segmentation along the producing zone. Experience has shown uncertainty with sealing washout and low-compressive-strength holes. Because of this, operators typically cement the well, therefore, affecting the productivity of the well by reducing the exposed formation area.

Effect of Completions on Horizontal Well Fracturing

The horizontal well fracturing has been of vital importance for the economic exploitation of oil and gas reservoirs with low and ultra low permeability. The process includes injecting a fluid at high pressure in a predetermined interval to generate as many possible fractures and of greatest extension in the producing formation. Preferably, horizontal wells are oriented in the direction parallel to the least in-situ principal stress. Thus, the fractures generated in this type of well will be perpendicular to the borehole axis. The fluid to create the fracture is generally mixed with a proppant material to maintain the fracture open for a longer period. Over the last decade, the advance of downhole fracturing has allowed to create larger number of fractures in longer horizontal wells. The fractures can be created in open-hole or cased hole completions.

Experience has shown that in open-hole completions the fractures tends to propagate initially longitudinally, sometimes causing a fracture extension across the open-hole packers. Additionally, there is a strong evidence that the sealing balls used for separating the fracture stages tend to break, impairing the fracturing process for some segments, and therefore, hindering the production potential of the well. Two basic type of completions are frequently used in horizontal wells are open-hole with liner, or cemented casing or liner.

Open-hole Liner Completions

Continuous Fracturing Systems: This is a frequent method used for extended reach wells in deeper formations. The objective is to create multiple hydraulic fractures in single and continuous pumping operations. The most common setup uses multiple frac ports opened individually by sliding sleeves that are activated hydraulically when a spherical ball of a diameter falls in the corresponding ball seat. Daneshy (Daneshy, 2011) shows a schematic of open-hole liner completion activated by ball drop. According to Daneshy, this type of completion has some benefits and disadvantages.

Benefits:

-   -   1. Faster and possibly less expensive completion and fracturing         operation.     -   2. Higher production from the exposed open-hole.     -   3. Less occurrence of screen-out, a condition that occurs when         the solids carried by the treating fluid, such a proppant in the         carrier fluid, create a bridge across the perforations or         similar restricted area.     -   4. Faster depletion of the near wellbore caused by the axial and         transverse fractures.

Disadvantages:

-   -   1. In case of longitudinal fracture initiation, it is very         likely for the fractures to cross the open-hole packers and         extend to the next interval. In a case study not included on         this disclosure, proppants used in various stages were traced.         Logging determined the presence of contamination in adjacent         intervals.     -   2. The ball drop completion systems are not suitable for         re-fracturing for the presence of the ball seats inside the         liner.     -   3. Some balls are made from dissolvable materials that later         allow to gain circulation through the ball seats. Sometimes the         ball does not dissolve, and circulation is not possible.     -   4. Complex solution for screen-out when there is no possibility         to re-enter the stage to clean the clogging due to the ball seat         restriction.     -   5. Limited injection rate due to the friction pressure exerted         by several ball seats.

FIGS. 6A-6D show a process of open hole completion. FIG. 6A shows drilling a portion of a well leading to a step prior to an open hole completion. FIG. 6B shows a casing that can for example be set above a zone of interest. The zone can be open to the well bore. FIG. 6C shows a perforated casing. In this example, performing an open hole completion includes setting the casing in place and perforating the casing, for example, to allow for production or various other drilling operations.

Use of MRF For Multistage Fracturing

For continuous fracturing systems (fracturing ports with sliding sleeves), the disadvantages 2, 3 and 5 previously described could be surpassed with the use of MRF valves. In that context, instead of using balls to fall into a ball seat, among other activation mechanisms, and create the seal to increase pressure and activate the sliding sleeve, an MRF could travel through a magnetic field and create a full seal inside the casing or in the annulus of workstring-casing. There can be various ways to activate or deactivate the valve, including:

-   -   1. Smart completions: Using electromagnets at different depths         that could be activated and deactivated with telemetry,         including pressure wave signals or electronic. In this case,         later with time this technology would allow to refracture the         well by gaining full hydraulic access to each of the sliding         sleeves.     -   2. Permanent Magnets and MRF concentration tuning: As an         alternative option, permanent magnets could be located at a         pre-set depth. These magnets could have different magnetic field         strengths. For example, the deeper the greater the magnetic         field. Since fracking is usually performed from bottom to top, a         MRF is pumped ahead with the proppant material, starting from         bottom to top with the lesser concentration of CIP. In such         case, the expected behavior is that the MRF travels inside the         casing through weak magnets that do not create a full seal, but         when they reach a stronger magnetic field (the one at the         bottom), a full seal is created. Hence, the latest MRF to be         pumped should have the highest CIP concentration to be capable         to create enough seal in front of the weak shallower magnets.

FIGS. 6D-6H illustrates another example. In this example, a process of multistage fracturing is shown. To illustrate the process, FIG. 6D shows a casing that can for example be set above a zone of interest. The zone can be open to the well bore. The casing in this example includes multiple sliding sleeves in various configurations relative to the open hole. The operation of this example includes affixing one or more permanent magnets that allow activation or deactivation of a valve. The MRF can, using this example, travel through the magnetic field and create a full seal inside the casing.

FIG. 6E shows pumping MRF down the work-string (tubular). The MRF is combined with a first grade of CIP. In this example, a magnetic field generated by the permanent magnets activates the MRF and creates a first full seal inside the casing. In this example, the first grade of CIP is a lowest grade CIP.

In one example operation, FIG. 6F shows opening a first sliding sleeve after the first full seal has been created. Opening the first sliding sleeve exposes a first frac port.

FIG. 6G shows pumping MRF down the work-string (tubular). The MRF is combined with a second grade of CIP. In this example, a magnetic field generated by the permanent magnets activates the MRF and creates a second full seal inside the casing. In this example, the second grade of CIP is a medium grade CIP. Not depicted is the opening of a second sliding sleeve after the second full seal has been created. Opening the second sliding sleeve exposes a second frac port.

FIG. 6H shows another example of pumping MRF down the work-string (tubular). The MRF is combined with a third grade of CIP. In this example, a magnetic field generated by the permanent magnets activates the MRF and creates a third full seal inside the casing. In this example, the third grade of CIP is shown as a lowest grade CIP. Not depicted is the opening of a third sliding sleeve after the third full seal has been created. Opening the third sliding sleeve exposes a third frac port.

In this example, performing a multistage fracturing operation can allow for production or various other drilling operations.

Use of MRF as Open-hole Packers for Well Completions

FIG. 6I illustrates a sixth example that includes depicts an apparatus that can be run along a wireline to create an open-hole MRF packer. FIG. 6J illustrates a modified sixth example. In this example, the illustration depicts an apparatus that can be used with tubing to create an open-hole MRF packer.

Use of MRF Packers for Water and Gas Shutoff Conformance

It is common that during the production of a well, unwanted water or gas production can occur. The reservoir thermodynamics and the drive type mechanisms are factors to determine if that problem will be encountered. Conformance is known as the technology offered to reduce the amount of water (or gas) produced be the well. The state of the art of conformance relies on crosslinked polymers that in contact with water produce a seal of the problematic zone. This technology exhibits environmental limitations that is limiting their use. Other problems include thermal instability.

MRF Packers are proposed as a mechanical barrier to isolate the zones were unwanted gas and water is being produced. FIG. 7 illustrates an example. In this example, MRF Packers are proposed as a mechanical barrier to isolate the zones where unwanted gas and water is being produced. FIG. 7 shows balancing or bullheading (pushing down) MRF to the producing formation covering the gas/oil/water sand-face. The illustration depicts running, using a wireline or slick-line, a set of magnets that will activate the MRF. The MRF will solidify in front of the problematic zone with the depth accuracy that the wireline or slick-line can provide. The CIP grade for this application is hard, to produce the electromagnetism to activate the MRF but giving enough room to retrieve the magnets. In this way, shown is an example of a full seal magneto-rheological down-hole packing element as a mechanical barrier to isolate unwanted water or gas according to various examples described herein.

Use of MRF Packers for Plug and Abandonment (P&A)

When a well is not currently profitable, the operators can decide to abandon the well temporarily or permanently. Nowadays, the oil industry is facing its busiest times on plug and abandonment of their wells. Under US Law, 30 CFR 250 establishes guidelines for decommissioning activities. The state of the art relies on cement slurries placed in the well in order to:

-   -   g. Provide downhole isolation of hydrocarbons and sulfur zones.     -   h. Protect freshwater aquifers.     -   i. Prevent migration of formation fluids within the wellbore or         to the seafloor.

30 CFR 250.1715 describes how a well can be abandoned according to the specification. Technology opportunities appear in multiple annuli to properly abandon. The fact that individual sections may have been drilled with different mud weight makes the fluid segregation a severe problem to properly set a cement plug. MRF is proposed as an alternative to accurately place the cement at the right depth.

FIGS. 8A-8B illustrates an example. To introduce the concept, FIG. 8A shows a fluid segregation during a conventional approach using a cement slurry. Because of the fluid segregation due to the density difference between the mud and the cement slurry, the placement accuracy can be diminished and potentially not comply with the regulation.

FIG. 8B shows an approach with MRF Technology. The multiple annuli are perforated to communicate among the multiple annuli. The approach depicted can include pumping a cement slurry generally through one of the annulus for what is called inversed circulation. With the fluid reaching the perforations, this approach can include the fluid filling the different annuli that are interconnected through the perforations. In contrast to the fluid segregation in a conventional approach, the proposed technology uses a mechanism and placing it beforehand. The mechanism can include arranging a set of magnets. Applying the mechanism can activate the MRF slurry in the annuli creating enough solidification to set at the designated depth. As an example, an approach can include running the mechanism using a wireline. In this way, shown is an example of a full seal magneto-rheological down-hole packing element to set at a designated depth in a plug and abandonment operation according to various examples described herein.

Selective-Resettable Zonal MRF Packers

External casing packers are permanent; however, the nature of the reservoir makes the contacts (Oil/Gas/Water) to move along the well. Additionally, the wells need to be refractured when the productivity decreases. These needs make convenient to be capable to re-set external casing packers. With the current technology this is not possible, especially when swellable rubber packers are used. With MRF resettable packers this could be possible. The MRF packer is activated when the magnetic field is applied to the fluid. A tool with permanent magnets is placed with a coil tubing set or wireline to activate a MRF in the annulus. Later, after production, the tool with the magnets can be retrieved. When no magnetic field is applied, the MRF packer becomes fluid. To achieve another selective production configuration, the MRF can be squeezed to the annulus and another permanent magnet assortment placed in the new location.

In the context outlined above, FIGS. 9A-9B shows an example of setting a selective-resettable zonal packer using MRF. The process of placing a zonal packer can include the equipment and operations previously discussed at FIGS. 6A-6C, among other places, including a perforated casing.

FIG. 9A illustrates running an apparatus that along a wireline to create a zonal packer. The apparatus can include a wireline with permanent magnets. In alternate examples, the apparatus can include coiled tubing with permanent magnets. The permanent magnets can be configured to apply a magnetic field to MRF, and to be retrieved after production. In this example, the illustration depicts causing the magnets to apply a magnetic field to the MRF to create a zonal packer. The figure shows a perforated casing, as previously described in FIG. 6C, that contains several opening ports that can allow fluid flow. The selective-resettable zonal packer in this example is shown as a zonal packer in that has isolated contacts (e.g., Oil/Gas/Water) in a first configuration.

In another example, FIG. 9B illustrates setting a zonal packer in a second configuration. Here, the well can be refractured when the productivity decreases. The figure depicts running the wireline with permanent magnets attached to place the magnets in a new location. The process can include squeezing the MRF to the annulus. The MRF packer is activated by applying the magnetic field to the fluid. The selective-resettable zonal packer in this example is shown as a zonal packer that has isolated contacts (e.g., Oil/Gas/Water) in a second configuration. In this way, shown are examples of full seal magneto-rheological down-hole packing elements as selective-resettable zonal packers according to various examples described herein.

Examples of Magnet Arrangements, Magnetic Field Generation, Packing Mediums, and Packing Mechanisms

Placing a magnetic assembly tool to apply a magnetic field to a flow of magnetorheological fluid can allow for the yield stress of the fluid to be varied downhole. Often in the oil and gas industry, a term called “gel strength” is reported in addition to yield strength for a fluid's rheology. These terms are [usually] correlated strongly and directly. In this context, the magneto-rheological effect refers to a change in either one of these properties or both. These downhole yield stress (and/or gel strength) variations, which can be up to several orders of magnitude, allow for the creation of pressure drops within the annulus that act like “pseudo downhole chokes.” The creation of this effect is not limited to a variation in yield stress (and/or gel strength) of the fluid; a similar effect can be obtained by a change in the “plastic viscosity” of the fluid or by a combination of the two effects. The property “plastic viscosity” refers to the rheology that fluid displays at higher shear rates. These increases in yield stress, and/or gel strength, and/or plastic viscosity can occur over a desired interval, and correspond with a length of a magnetic assembly tool (or an arrangement of magnets on the magnetic assembly tool). A magnetorheological drilling fluid can be created through the replacement of traditional weighting materials with ferromagnetic weighting materials. Using the aforementioned pseudo downhole chokes, the operator can control the influx from a shallow gas well without exceeding downhole pressure limits, at multiple points, predetermined by shallower formation integrity.

A system that includes a magnetic assembly tool and a magnetorheological drilling fluid can enable to safely drill these formations when influx and pressure control methods such as closing a blowout preventer (BOP) would be unfeasible due to the characteristics of the weaker formations in the open hole which could result in underground blowouts or loss of hole. Another proposed use for this system is to navigate tighter mud weight windows typically seen at greater depths in ways that cannot be accomplished with current managed pressure drilling technology in order to extend casing setting points. This can allow for the drilling to hydrocarbon bearing formations that were previously unobtainable due to the complicated mud windows involved. Magnetorheological fluids can be applied in drilling systems for annular pressure control in challenging situations.

A system that includes a magnetic assembly tool and a magnetorheological drilling fluid can allow for a yield stress, or other rheological properties of the fluid as described in [0092], of the fluid to be varied downhole to result in one or more pressure drop(s) of determined length and magnitude. In one example, the system described herein can include a magnetic assembly tool and a magnetorheological fluid. When placed, the magnetic assembly tool can apply a magnetic field to a flow of the magnetorheological fluid. Applying a magnetic field can then create a semi-solid packing element that is based on a build-up of the magnetorheological particles of the magnetorheological fluid that are near the magnetic field. Applying a magnetic field can also create a magneto-rheological effect based on an alignment of magnetorheological particles with the magnetic field. Thus, applying the magnetic field can result in a partial seal or a full seal.

Placing the magnetic assembly tool can achieve a purpose including to release a differential sticking, to form a seal in a sub-pressurized formation, to allow several stages of hydraulic fracturing, to create a selective-resettable zonal packer, to isolate gas or water, or to set at a designated depth in a plug and abandonment operation. The system can include placing the magnetic assembly tool in a drill pipe or a hole. The system can also include placing (and/or) embedding an arrangement of the magnetic assembly tool outside a drill pipe. In some examples, the magnetic assembly tool comprises an arrangement of a plurality of magnets, and the placing the magnetic assembly tool comprises embedding the arrangement inside a casing.

Various examples of the system(s) described herein can create a partial seal or a full seal, and can include a partial seal or a full seal between a pipe and an annulus. Additionally, placing the magnetic assembly tool to create a full seal can include creating a full seal in a plurality of annuli.

Examples of the present disclosure include a magnetic assembly tool. In one example, a magnetic assembly tool can include an arrangement of at least one of a plurality of magnets configured to alter at least one of a plurality of rheological properties of a region of a flow of a magnetorheological fluid. The at least one of the plurality of magnets can for example include a permanent magnet, an electromagnet, or a magneto-elastic magnet.

The arrangement can include a ring, a segmented ring, a multi-segmented ring, or a spiral. The magnetic assembly tool can further include an orientation of the at least one of the plurality of magnets configured to create a magnitude and orientation of a magnetic field to alter the at least one of the plurality of rheological properties. The magnetic assembly tool can also be configured to generate a packing mechanism that can include a radial packing or a lateral packing.

In some examples, the arrangement of the magnetic assembly tool is configured to be placed in a drill pipe, a casing, or a hole. The arrangement can be a ring, and the orientation can include a dipole of each one of the at least one of the plurality of magnets oriented in a same radial direction. The arrangement can also be located on a tubing, a wireline, or a bottom-hole assembly (BHA). In other examples, the magnetic assembly tool can include an attachment configured to locate the at least one of the plurality of magnets on a downhole tool. The downhole tool can include a tubing, a wireline, or a bottom-hole assembly (BHA).

Examples of the present disclosure include a magnetorheological fluid. A magnetorheological fluid (MRF), also described as a magnetic field responsive fluid, is a combination of magnetically polarizable particles in a carrier fluid. A MRF is a fluid whose rheological properties, specifically its yield stress, can be altered when under the influence of a magnetic field. This type of fluid has the ability to modify its rheological properties under the influence of a magnetic field. The generation of a tunable pressure drop can control fluid losses while drilling and cementing in narrow operating windows and to provide a tunable fluid barrier that works as a packer. Using the reduced form of the Navier-Stokes equation and a model to estimate the yield stress of the fluid based on the magnetic field strength, it is possible to determine the pressure drop caused by the fluid behavior. A magnetorheological drilling fluid can be created by changing all, or just a portion, of a weighting material of a drilling fluid from barite to iron particles.

A magnetorheological fluid can include a suspension of magnetizable particles in a liquid. The liquid can include a drilling fluid, and the magnetizable particles can include an iron powder. The magnetorheological fluid can thus be a mixture of a carrier fluid, magnetic (or magnetizable) particles and a viscocifier (or stabilizer) to avoid the sedimentation of the particles.

The iron powder can be a soft grade Carbonyl Iron Powder (CIP) or a hard grade CIP. The CIP can be an iron powder manufactured through thermal decomposition. A factor for the design and stability of MRF is the magnetizable particle size. The range of between about 0.1-10 μm may be an optimum size to prevent particle sedimentation due to the unusually high density (7.5 g/cm3) of the particles. Carbonyl Iron Powder (CIP) can be used as a magnetizable particle to prepare MRF.

The magnetorheological fluid can also include a viscocifier agent and/or a carrier fluid. A viscocifier agent (or stabilizer) can be an additive that is aggregated to the MRF to prevent the magnetizable particle settling and to modify the initial viscosity of the MRF. Examples of the viscocifier agent include a clay, a polymer, or a biopolymer. For example, Bentonite is a natural and industrially available clay. Other stabilizers include synthetic colloidal clay Laponite RD, non-polar Polyalphaolefin (PAO), Dioctyl Sebacate (DOS), Carbonyl Methyl Cellulose (CMC), or Xanthan Gum Kelzan.

The carrier fluid can be a continuous phase in which the magnetizable particles are suspended. One aspect in selecting a carrier fluid is that it be thermally stable, non-corrosive, non-reactive to the magnetizable particles, cost-effective and environmentally friendly. Examples of a carrier fluid include a petroleum-based oil, a mineral oil, water, a paraffin oil, a silicon oil, a polyether, a glycol, a drilling fluid, or a cement slurry.

FIGS. 10-26 show examples of types of magnet arrangements, types of magnetic field generation, magnet arrangement locations, packing mediums, and packing mechanisms according to various example embodiments described herein. Various scenarios are disclosed that allow a magnetic field to be generated. In these scenarios, magnets can be embedded or attached during drilling practices of flowing down an inner drill pipe and circulating up the annulus.

FIGS. 10-13 show examples of magnet arrangements according to various example embodiments described herein. As mentioned before, MRF can activate under the influence of a magnetic field because the magnetic particles align in its direction. FIG. 10 shows a type of magnet arrangement 1003 that is a magnet ring. The magnet ring can include for example one or more magnets 1006 that have a range of diameters and a range of lengths that can be effective for placing a down-hole packing element.

Any of the examples of magnet arrangements shown in FIGS. 10-13 can be attached to or embedded in a tool 1009. A magnet arrangement can be embedded in or attached to a tool 1009 or other component such as a coil tubing set or wireline. The magnet arrangement 1003 that is the magnet ring can for example be embedded on a pipe with a pre-established diameter and length. The magnet ring can be protruded or not. Another example is to embed a magnet arrangement in or attach a magnet arrangement to a bottom hole assembly (BHA).

In one example, the magnet arrangement 1003 was embedded or attached to an inner drill pipe (workstring). The magnet arrangement 1003 was used in an experimental setup (FIG. 27) that will be described in more detail in a section below. The magnets 1006 were aligned into 2 smaller rings of approximately 0.2 inches axial length each, and 2 larger rings of approximately 0.79 inches axial length. The magnets 1006 can be neodymium ring segment magnets and coated in nickel. The magnets 1006 can be grade N45H or higher, depending on the magnetic field strength preferred. The first (upstream most) magnet arrangement 1003 can be composed of small magnets 1006 arranged such that their south magnetic dipoles were facing outwards into the annular flow area. The next magnet arrangement 1003 can also be composed of small magnets 1006, but arranged such that their north magnetic dipole were pointed into the annular flow area. The next two magnet arrangements 1003 can be of the larger magnets 1006 and arranged such that the upstream magnet arrangement 1003 had its north magnetic dipole pointed into the annular flow area and the downstream most magnet arrangement 1003 had its south magnetic dipole pointed into the annular flow area. These magnet arrangements 1003 occupied an axial length of only 6 inches in total.

As described, a magnet arrangement 1003 (or magnet ring) can include a plurality of magnets 1006 making up a segment of the magnet arrangement 1003. The segments can be arranged so that all the magnets 1006 on a ring have their dipoles oriented in the same radial direction to prevent magnetic fields from different dipoles meeting and canceling out. The same logic can be applied for rings which have dipoles pointed into the annular flow area.

The strength of magnetic rings in some examples ranged from around 3000 Gauss on the outside of the epoxy coating to near 450 Gauss at ½ an inch radially outwards for the larger magnets. The strength near the epoxy was similar for the smaller magnets, but their strength at ½ an inch radially outward was closer to 50-60 Gauss.

FIG. 11 shows a magnet arrangement 1012 that is a segmented ring that can include a plurality of magnets 1015. The plurality of magnets 1015 can be attached so there is a distance 1018 between adjacent magnets 1015. The magnet arrangement 1012 can include the plurality of magnets 1015 being equally spaced around a circumference of a tool 1009. The magnet arrangement 1012 that is a segmented magnet ring can be a pre-established diameter and length, with or without protrusion.

FIG. 12 shows a magnet arrangement 1021 that is a multi-segmented ring that can include a plurality of magnets 1024. The plurality of magnets 1024 can be attached so there is a radial distance 1018 between adjacent magnets 1024. The magnet arrangement 1021 can include the plurality of magnets 1024 being equally spaced around a circumference of a tool 1009. Also, the magnets 1024 can be attached so there is an axial distance 1027 between a first segmented ring of magnets 1024 and a second segmented ring of magnets 1024. The magnet arrangement 1021 that is the multi-segmented ring can comprise several magnet rings spaced one to each other. The diameter, length, gap length, segmented or continuous, protruded or not, are possible variations to its design.

FIG. 13 shows a magnet arrangement 1030 that is a spiral that can include a plurality of magnets 1033. The plurality of magnets 1033 can be attached so there is a distance 1036 between adjacent magnets 1033. The magnet arrangement 1030 can also include the plurality of magnets 1033 being equally spaced. As shown in the cross section view depicted in FIG. 13, the magnets 1033 can be arranged at equal angular intervals on a circumference around a tool 1009. The lateral view shows that each one of the magnets 1033 can have a length 1039. The magnet arrangement 1030 can include the magnets 1033 being arranged so that each one of the magnets 1033 is offset by a distance about equal to the length 1039. Any of the magnet arrangements 1003, 1012, 1021, or 1030 can be attached to or embedded in a tool 1009, a drill pipe, or a component such as a coil tubing set or wireline as can be appreciated.

FIGS. 14-16A show examples of magnetic assembly tools 1103, 1106, and 1109 for generating magnetic fields according to various example embodiments described herein. Rheological properties on MRF can be tuned according to the magnitude and direction of the magnetic field applied to it. A magnetic field can be applied by setting a magnet arrangement 1003, 1012, 1021, or 1030. FIG. 14 shows a magnetic assembly tool 1103 can include a downhole tool 1009 with a magnet arrangement 1003, 1012, 1021, or 1030 comprising one or more permanent magnets 1045 embedded.

FIG. 15 shows a magnetic assembly tool 1106 can include a downhole tool 1009 with a magnet arrangement 1003, 1012, 1021, or 1030 comprising one or more one or more electromagnets 1051 embedded. In this example, the electromagnets 1051 can receive power from a source that is located at the surface or can receive power from a downhole assembly 1112 (FIG. 16B).

FIG. 16A shows a magnetic assembly tool 1109 can include a downhole tool 1009 with a magnet arrangement 1003, 1012, 1021, or 1030 comprising one or more magneto-elastic magnets 1057 embedded. The magneto-elastic magnets 1057 can be used along with applying or varying a weight (compression) or a tension to the tool 1009, which is usually controllable on a rig by a draw-work (and other parts of a rig's hoisting system) at the surface. Thus, depending on the tension or weight applied to the magneto-elastic magnets 1057, an intensity of the magnetic field can be modified at the surface without the need for telemetry equipment.

Referring now to FIG. 16B, shown is a downhole assembly 1112 of a magnetic assembly tool. The downhole assembly 1112 can transform kinetic energy of flowing/circulating fluid through a downhole turbine into electric energy via a generator. The generator can produce a magnetic field when a flow rotates a rotor of the downhole assembly 1112.

A magnetic assembly tool such as the magnetic assembly tool 1103, 1106, or 1109 shown by FIGS. 14-16A can provide the ability to modify rheological properties of the MRF and generate a tunable pressure drop. The generation of a tunable pressure drop can (among other things) control fluid losses while drilling and cementing in narrow operating windows, and can provide a tunable fluid barrier that works as a packer.

The ability of a magnetic assembly tool 1103, 1106, or 1109 to create a tunable pressure drop has been validated. The magnetic assembly tool 1103, 1106, or 1109 allows for modification of viscosity downhole. Magnetorheological fluid can be created through the replacement of API barite with iron microspheres that are round and smooth. The iron particles can be synthetically created iron microspheres. The diameters of these particles can range for example from 1 to 10 micrometers. The particles can be uncoated and almost entirely pure iron.

When a magnetic field is applied, the iron particles align themselves with the magnetic field and create a barrier to flow. The particles are attracted to each other due to the magnetic dipoles they obtain while under the influence of the magnetic field, resembling a chain of particles. The strength of this effect can be dependent on the strength of the magnetic field, as well as the volume percent of ferromagnetic materials, as described in “Magnetorheological Fluids. Journal of Magnetism and Magnetic Materials” Volume 252. (2002) by Bossis, G., Lacis, S., Meunier, A., Volkova, O.

In tests in a flow loop (shown in FIG. 27), potential mud samples were mixed at lab scales (350 mL samples) in order to determine reasonable amounts of viscosifying agents and weighting materials to be added for larger experiments. This was done through the creation and testing of water based version of both more traditional bentonite/barite muds as well as the magnetorheological bentonite/iron muds. Samples were created using and tested using API 13B-1 standards with a Fann 35 A rotating bob viscometer.

350 mL of soft water was mixed with different amounts of bentonite for 10 minutes. These mixtures were then allowed to sit and hydrate for 24 hours before being mixed with their respective weighting materials. Weighting materials of either barite, or iron microspheres were then added to the hydrated bentonite samples and allowed to mix for an additional 10 minutes. All mixing took place in a drink mixer at the mixer's 17,000 rpm setting.

Sample Information Name Bentonite Barite Iron Sample 0.2 30 g 48 g 0 Sample 1 30 g 0 41.53 g Sample 2 25 g 0  41.6 g Sample 3 20 g 0 41.51 g Sample 4 20 g 0 82.16 g Sample 6 23 g 0 41.08 g Sample 7 23 g 0 41.03 g Sample 8 23 g 0 41.14 g Sample 9 23 g 0   41 g Sample 10 23 g 0   41 g Flow Loop 23 lbs./bbl. 0 41 lbs./bbl.

Sample 0.2 was designed to have a base reading to compare the magnetorheological fluid against.

A larger 55 gallon sample was mixed for use in the flow loop using 23 lbs./bbl. bentonite and 48 lbs. (pounds)/bbl. (barrel) barite. The reason for using a different amount of bentonite for the flow loop sample was so that the amount of bentonite would be the same in both the “normal” and the magnetorheological fluids in order to simulate replacing the barite with iron.

Multiple samples of iron microspheres and bentonite were created using 23 grams of bentonite and 41 grams of iron particles per sample.

Electron Dispersive Spectrometer (EDS) quantitatively examined the elements present and confirmed that the iron particles were indeed embedded in the bentonite, and did not show significant chemical changes otherwise.

Data for EDS Spot 3:

Element Weight % Atomic % Error % O K 26.09 49.83 6.30 MgK 1.20 1.50 9.06 AlK 5.45 6.17 6.04 SiK 13.32 14.50 4.89 PtM 3.88 0.61 5.80 FeK 50.07 27.40 2.65

The magnetorheological fluid was tested in an actual flow loop (FIG. 27) under the influence of a magnetic field. This was done through the use of an inner pipe with permanent magnets and an outer pipe to create an annulus.

Pressure transducers were set up, equidistant, both upstream and downstream of the magnets. The pressure difference between these pressure transducers allowed for a qualitative analysis of the difference between the bentonite/barite and magnetorheological fluid as the fluids weights were increased.

Fluid Test Results Gel Strength Sample Names Density Viscosity Yield 10 s. 10 min. Sample 0.2 9.35 9.5 13.5 4 11 Sample 1 9.35 14.5 33 8 21 Sample 2 9.4 13 27 8 19 Sample 3 6 9 4 6 Sample 4 10.15 9 13.5 4 9 Sample 6 9.35 9 16 5 9 Sample 2 19 28 7 16 Sample 7 9 14 4 9 Sample 8 9 17 4 9 Sample 9 8 16 4 Sample 10 9.5 16 4.5 Flow Loop 9.3 13 16 4 9

A mud tank was filled to pre-determined levels and then bentonite was added and allowed to mix for 24 hours. The mixer for the mud tank was turned on to its 1750 rpm rating. As previously mentioned the amount of bentonite was approximately the same for each mixture, meaning that the only variable being changed was the type of weighting material being used. The amount of bentonite was approximately 23 lbs./bbl.

The barite was added in separate batches of 0.575 kg per batch, whereas the iron microspheres were added in batches of 0.5 kg per batch. These amounts were chosen so that the same number of batches were added in total during the experiments to reach the predetermined amount of weighting material to be added. All batches were pumped through the system at 20 gallons per minute. This gives an average annular velocity of 0.62 ft./s

Referring now to FIG. 16C, the pressure difference between the two middle pressure transducers (FIG. 27) was plotted against the batch number for both weighting materials. From these results we can see that after enough weighting material has been added (4 batches in our case) a gap develops between the differential pressure seen in the barite experiments and the differential pressure seen in the magnetorheological fluid experiments. Except for an anomaly around 10 batches, this differential pressure gap increased in size up to a maximum near 20 batches.

The drop in pressure seen from 8 to 10 batches for the magnetorheological fluid is likely tied to the fact that those test took place on different days. It is therefore likely that some change in the fluid had occurred. The drop seen from batches 11 to 13 for the barite based fluid occurred across all pressure transducers, and not just across the magnet area. This is also a potential explanation for the magnetorheological pressure change from 8 to 10 batches.

There is also a noticeable change in the pressure differential starting at 22 batches of iron microspheres. At this point the pressure becomes more dynamic. It is believed that this is the point where a saturation of iron particles has been reached for this particular setup. The results of this saturation would be a bridging of particles and start/stop phenomenon for the flow, where flow stops until a pressure builds up to break the particles apart and start the process over.

A 55 gallon flow loop sample had weighting material added until it reached 23 lbs./bbl. of bentonite and 41 lbs./bbl. of iron microspheres. This flow loop sample was created over the course of 6 days. On the 7th day, a small 350 mL sample was taken from this to be tested in the lab. All of the rheological and density values were consistent with the previously created lab samples, except for the higher 13 cp plastic viscosity.

It has been shown that a magnetorheological drilling fluid with stable properties can be created. It has also been shown that a drill pipe can provide enough magnetic shielding to allow for a magnetic field to be created in the annulus without affecting the fluid inside the drill pipe.

FIGS. 17-19 show locations for magnet arrangements according to various example embodiments described herein. A location for a magnet arrangement refers to a position and location of the magnetic source—or magnet arrangement downhole—to produce the desired effects on the MRF.

FIG. 17 shows a magnet arrangement such as magnet arrangement 1012 can be located inside a drill-pipe 1060. For example, the magnet arrangement 1012 can be embedded or attached to a tool 1009 to create a packing effect on a medium. The magnet arrangement 1012 is in a tool 1009 that is run downhole inside the drill-pipe 1060. It is interpreted that the drill-pipe 1060 can totally or partially shield a magnetic field.

FIG. 18 shows a magnet arrangement 1012 can be located outside a drill-pipe 1060 or bottom hole assembly (BHA). A magnet arrangement 1012 outside a drill pipe 1060 can create a packing effect on a medium. For example, a drill pipe 1060 with a magnet arrangement 1003, 1012, 1021, or 1030 embedded (or attached) as shown in FIGS. 17 and 18 can be used to generate a tunable pressure drop in an annulus. For example, one or more packers can be created to withstand the hydrostatic pressure above it. The pressure below the packer can be modified (e.g., reduced) locally to decrease a differential pressure.

FIG. 19 shows a magnet arrangement (e.g., magnet arrangement 1012) can be located inside a casing 1063. The casing 1063 can be run into a drilled well. A casing 1063 with the magnet arrangement 1012 shown in FIG. 19 allows a magnetic field to be applied to active MRF in multiple regions to create one or more full seals inside the casing 1063. The magnetic arrangement 1012 depicted in FIG. 19 is located inside the casing 1063 at multiple locations that can be spaced out from a few inches to several feet apart. It is interpreted that the casing 1063 can totally or partially shield a magnetic field.

In operation, the magnet arrangement 1012 can include a plurality of magnets inside the casing 1063. Magnets 1015 and magnets 1066 are opposite each other and in a first region of the casing 1063. Magnets 1069 and magnets 1072 are opposite each other and in a second region of the casing 1063. A system that includes a magnetic assembly tool 1103, 1106, or 1109 can place the magnet arrangement 1012 inside the casing 1063 as depicted in FIG. 19. When placed, the system can apply a magnetic field to a flow of the magnetorheological fluid to create a packing medium as will be further described with regards to FIGS. 20-24.

Next, FIGS. 20-24 show examples of packing mediums according to various example embodiments described herein. A packing medium refers to a medium in which MRF can produce a packing, sealing, or blocking effect. As mentioned before, this is envisioned to occur when an MRF is in contact with a magnetic field. In that sense, an arrangement location can also determine the packing medium.

FIG. 20 shows a magnet arrangement 1003 outside the drill pipe 1060 can be used to create a packing medium 1078 for packing a region between the pipe 1060 and the annulus 1075. FIG. 21 shows a magnet arrangement 1003 inside the drill pipe 1060 can be used to create a packing medium 1078 for packing a region between the annulus 1075 and the drill pipe 1060.

FIGS. 20 and 21 show a packing medium 1078 for packing a region between the pipe 1060 and the annulus 1075. The packing medium 1078 as depicted can be a total or partial blockage of the annular space between the outside of the drill-pipe 1060 or BHA and the open-hole (subterranean formation) when a magnetic arrangement 1003, 1012, 1021, or 1030 is located inside the drill-pipe 1060 (FIG. 21) or outside the drill-pipe 1060 (FIG. 20)

For example, a magnetic assembly tool 1103, 1106, or 1109 can apply a magnetic field to a flow of magnetorheological fluid to create a seal that partially packs a region with a packing medium 1078. The packing medium 1078 can be outside of the drill pipe 1060. MRF can flow between the drill pipe 1060 and the annulus 1075. While FIGS. 20 and 21 depict an example with a partial packing, the packing medium 1078 can also completely pack the region between the pipe 1060 and the annulus 1075 according to other examples.

FIG. 22 shows one or more magnet arrangements 1003 attached at various points along an inner side of a casing 1063 can be used to create a packing medium 1078 for packing multiple regions inside the casing 1063. The packing medium depicted in FIG. 22 can create one or more full seals. For example, MRF can be pumped down a work-string (tubular). The MRF can be combined with a first grade of CIP to create a first full seal 1081 inside the casing 1063. The MRF can also be combined with a second grade of CIP to create a second full seal 1084 inside the casing 1063, and so forth. As such, the packing medium 1078 of FIG. 22 refers also to the blockage, partial or total, of the space inside a casing 1063.

FIG. 23 shows a packing medium 1078 for packing a formation 1087. FIG. 23 shows examples of the present disclosure can be used to pack a formation 1087. The example of FIG. 23 depicts that a packing medium 1078 can include a first region 1090 that is inside the formation 1087, and a second region that is outside the formation 1087. The formation packing can be partial or complete. In operation, a magnetic assembly tool 1103, 1106, or 1109 can be placed in a drill pipe 1060 that is in the hole to relieve a pipe that is stuck to a formation 1087 in the hole. Placing a magnetic assembly tool 1103, 1106, or 1109 in the drill pipe 1060 can form a seal (depicted as packing medium 1078 in the first region 1090 and packing medium 1078 in the second region 1093) in a sub-pressurized formation 1087 to release a differential sticking.

The packing medium 1078 also refers to the blockage, partial or total, of the subterranean formation 1087 wall, also known as wellbore. The blockage can extend a few feet beyond the wellbore and/or protrude from the wellbore inside the hole.

FIG. 24 shows a packing medium 1078 for packing multiple annuli. Multiple casing strings 1096 can be run into a hole for packing multiple annuli. A packing medium 1078 can be between adjacent casing strings 1096. For example, FIG. 24 depicts three casing strings 1096. The packing medium 1078 can form a partial and/or full seal in the region 1097. The packing medium 1078 can also form a partial and/or full seal in the region 1099.

In operation, a magnetic assembly tool 1103, 1106, or 1109 can be placed in a hole to properly abandon a well. Placing the magnetic assembly tool 1103, 1106, or 1109 in a drill pipe 1060 can form one or more partial and/or full seals in a plurality of annuli. The multiple annuli can be perforated to communicate among the multiple annuli. The approach depicted in FIG. 24 can include pumping a cement slurry generally through one of the annulus for what is called inversed circulation. With the fluid reaching the perforations, this approach can include the fluid filling the different annuli that are interconnected through the perforations. A magnetic assembly tool 1103, 1106, or 1109 can be used to activate the MRF slurry in the annuli creating enough solidification to set at the designated depth. The packing medium 1078 refers to the blockage, total or partial, of different annuli present in the wellbore.

FIGS. 25 and 26 show examples of packing mechanisms according to various example embodiments described herein. A packing mechanism refers to how a packing medium can impede the crossflow of fluids such as: water, gas, oil, cement slurries, drilling mud. Also, a packing mechanism can refer to an ability to improve the placement accuracy of other fluids downhole.

FIG. 25 shows a packing mechanism 1203 that is a radial packing. A radial packing allows a packed region 1206 to have no flow from outside the formation into the hole, and vice-versa. FIG. 25 depicts the packing mechanism 1203 can also allow for a region 1209 and a region 1212 where there is flow from outside the formation 1087 into the hole. The radial packing can be accomplished by placing a magnet arrangement 1003, 1012, 1021, or 1030 of a magnetic assembly tool 1103, 1106, or 1109 inside a hole. As such, the packing mechanism 1203 can refer to the orientation and placement of the MRF to impede the flow of fluids inwards or outwards radially of the hole.

FIG. 26 shows a packing mechanism 1215 that is a lateral packing. The lateral packing creates a packed region 1218 that can stop or reduce flow, such as flow across a desired depth. The lateral packing as shown in FIG. 26 can also allow for regions 1221, 1224 where there can be flow. In operation, the lateral packing can be accomplished by placing a magnetic assembly tool 1103, 1106, or 1109 having a magnet arrangement 1012 inside a drill pipe 1060. For example, one or more packers can be created in the packed region 1218 to withstand the hydrostatic pressure above it. The pressure below the packed region 1218 can be modified (e.g., reduced) locally to decrease a differential pressure. As such, the packing mechanism 1215 can refer to the blocking of the fluid flow laterally in the well, that is from deeper to shallower, or from shallower to deeper depths.

Use of Magnetorheological Fluids for Pressure Drop Generation—Experimental Evaluation

FIG. 27 depicts an example of a schematic for an experimental setup according to various example embodiments described herein. In an experimental setup, different MRF samples were circulated on a well-like flow loop where the pressure drop of the fluid is measured in linear sections and compared to the models. The experimental setup also serves as a small-scale well where different applications for this type of fluid can be tested. An evaluation has been made to determine if a pressure drop can be generated when this fluid is exposed to a magnetic field.

The magnetorheological fluids (MRF) are well known by some other industries; their discovery is attributed to Jacob Rabinow in 1949; however, just in the recent decade this type of fluid has been used at an industrial scale.

Nowadays, they are providing a turning point in how fluid mechanics works. These “smart-fluids”, also known as magnetorheological fluids (MRF), include a suspension of magnetic particles in a liquid. Under the influence of a magnetic field, the suspended magnetic particles interact to form a new structure that resist shear deformation or flow. The interaction of these particles and the magnetic field creates a form of columnar structure that restricts the motion of the fluid, thus, increasing its rheological properties (as described in a paper by Kolekar, S. (2014). Preparation of Magnetorheological Fluid and Study on Its Rheological Properties. International Journal of Nanoscience, 13(2), 1450009 (1-6). https://doi.org/10.1142/S0219581X14500094). This feature has attracted some industries to use these fluids to overcome old engineering limitations. Some examples of the MRF applications are found in dampers, bridges, body armors and shock absorbers systems. Thus, as the MRF have revolutionized different industries and how the fluid mechanic works, the Oil and Gas Industry can benefit from using this type of fluid to provide solutions for drilling and completions operations.

The properties of the MRF are susceptible depending on 3 factors:

-   -   1. the magnetizable particles volume fraction (dispersed phase),     -   2. the carrier fluid (continuous phase) and     -   3. the strength of the magnetic field.

The fluid structure, once a magnetic field is applied, is accountable for the formation and reversibility from a free-flowing liquid to a semi-solid. The reversibility can be tuned for each application presented in this disclosure, some applications benefit from fast reversibility while others benefit from delayed reversibility. The reversibility can depend on the grade of the magnetizable particles available on the market, being Carbonyl Iron Powder (CIP) the one used for this research. The CIP is an iron powder manufactured through thermal decomposition and is one of the most common magnetic particle used for MR applications. Because of its high magnetic susceptibility, these particles align easily in the direction of the magnetic field. The commercialized CIP can be hard grade or soft grade. On the one hand, soft grade magnetic materials can be easily magnetized and demagnetized, which provides a better control over the MRF. On the other hand, hard grade magnetic materials can maintain the magnetized fluid structure without the presence of the magnetic field (as described in a paper by Hajalilou, A., Amri Mazlan, S., Lavvafi, H., & Shameli, K. (2016). Field Responsive Fluids as Smart Materials. https://doi.org/10.1007/978-981-10-2495-5). This characteristic is of vital importance because depending on the intended application, an appropriate magnetic material needs to be considered to create an immediate or delayed stiffening.

Another important factor for the design and stability of MRF is the magnetizable particle size. The range of between about 0.1-10 μm may be an optimum size to prevent particle sedimentation due to the unusually high density (7.5 g/cm3) of the particles. Carbonyl Iron Powder (CIP) can be used as a magnetizable particle to prepare MRF. Additionally, the particle size determines the chain-like formation on the SEM micrograms (Hajalilou et al., 2016). The chains are less stable in the micron size particles but well defined and structured in the nano size domain. The more regular the chain formation, the better the rheological response of the MRF.

Although the conventional drilling fluids in the oil industry have been used extensively for several decades, their rheological properties can only be set at surface by adding chemical additives and cannot be tuned once these fluids are pumped downhole. This imposes a limitation for these fluids, making any rheological change time consuming, non-immediately reactive and frequently expensive because of the high amount of volume to be treated with chemicals. Particularly, the rheology in Magnetorheological Drilling Fluids, which is the addition of magnetic particles to the conventional drilling fluid, are not chemically dependent. Furthermore, the change of the rheological properties of a MRF is tuned according to the intensity and direction of a magnetic field applied to the fluid (as described in a paper by Vryzas, Z., Kelessidis, V. C., Bowman, M. B. J., Texas, A., & Nalbantian, L. (2017). SPE-183906-MS Smart Magnetic Drilling Fluid With In-Situ Rheological Controllability Using. https://doi.org/10.2118/183906-MS). This feature allows that any rheological change can be achieved even downhole or at surface when a magnetic field of a certain intensity is applied to the MRF with fixed magnets or electromagnets (as described in a paper by Zitha, P. L. J., & Wessel, F. (2002). Fluid Flow Control Using Magnetorheological Fluids. Proceedings of SPE/DOE Improved Oil Recovery Symposium, 1-10. https://doi.org/10.2523/75144-MS). In addition, the possibility of a fluid creating a fluid barrier when a magnetic field is applied provides an advantage where potential application in the industry can be evaluated.

An experimental apparatus and experimental setup was used to evaluate the MRF behavior in a flow loop. The objective of the setup is to flow the MRF through two concentric pipes that simulate the workstring and the annulus of a well and determine how the pressure drop in the annulus is affected as a function of the magnetic field generated. Therefore, a modifiable magnet arrangement of Neodymium permanent magnets was placed in the workstring and fixed with a layer of epoxy. The magnet arrangement of the Neodymium magnets create a magnitude and orientation of the magnetic field and in consequence, an alteration of the rheology of the MRF.

TABLE 1 Magnetic Field [mTesla] Degrees Distance from the from the Small Small Large Large Uppermost Magnet S over N over N over S over Magnet Surface N S S N 0 0 322 108 N 313 N 325 45 0 298 162 N 288 N 290 90 0 273  99 N 278 N 270 135 0 234 112 N 325 N 260 180 0 241 108 N 280 N 365 225 0 255 124 N 300 N 270 270 0 216 190 N 318 N 310 315 0 264 180 N 308 N 300 0 0.25 14 *  60 N 63 0 0.5 6 *  45 N 40 0 0.75 5 *  31 N 25 0 1 4 *  15 N 13 0 1.25 6 *  17 N 16 0 1.5 4 *  11 N 12 0 1.75 2 *  9 N 7 0 2 1 *  6 N 3

Referring still to FIG. 27, the inner pipe (workstring) has an outside diameter (OD) of 1.66-in and inside diameter (ID) of 1.5-in. This pipe is made of carbon steel and the magnets were placed intentionally in the outer wall to evaluate if the magnetic field generates a rheology change only in the annulus while allowing the MRF to flow unaffected inside the workstring. The outer pipe representing the openhole is a stainless-steel pipe schedule 304 with an OD of 4.5-in and ID of 4.0-in. Four thredolets were welded on the outer pipe to install modular pressure transducers Honeywell FP2000 to read the pressure along the annulus. One additional pressure transducer was installed after the pump to read the drillpipe pressure. The permanent magnets arrangement is located equidistant in between transducers P3 and P4 (FIG. 27).

The pump selected to run the experiments is peristaltic Watson Marlow Bredel 40. In this type of pumps, the fluid is pushed from the inlet to the outlet through a hose squeezed by some rollers. This positive displacement pump can prevent the MRF to be in contact with moving parts to avoid any contamination. Also, this pump can allow a constant flow rate whilst the back pressure is altered. The later feature can help with establishing the relationship between the rheology and pressure drop developed by the MRF when flowing next to the magnets. The MRF was mixed in an 85 gal drum with 45 grades pitched blade turbine impellers. The electric motor for the mixer is located far enough from the MRF to avoid any premature activation. The MRF is pumped by the peristaltic pump and a pulsation dampener Blacoh C905ND is used to reduce the pressure pulsation. The MRF enters the drillpipe and is pumped through the annulus where the pressure transducers read the pressure drop. The MRF fluid reaches the outlet (flowline) and dumped to the mud tank to be circulated again to the system.

The MRF was prepared with Carbonyl Iron Powder. These particles have a purity of 99.5% (metal basis) and a specific gravity of 7.86 g/mL at 77° F. The CIP is also the weighing material for the sample fluid. Additionally, bentonite with a specific gravity of 2.5 g/mL was added as the viscocifier agent. The carrier fluid was fresh water. A general information of the sample fluid is presented on the following table:

TABLE 2 Fluid Characteristics Property Value Bentonite [wt %] 5.89 CIP [wt %] 0.44-10.5 Density Range 9.0-9.3 [ppg]

Referring now to FIG. 28, the rheologies of the MRF sample with CIP concentration of wt % 10.5 were measured at a rotational viscometer Fann 35 in the absence of any magnetic field as shown in FIG. 28. FIG. 28 depicts a Rheogram for MRF CIP wt % 10.5. The fluid was circulated in the experimental setup at the minimum concentration of CIP (0.44 wt %), the pressure drop was measured and recorded. The CIP concentration was increased sequentially until reaching the maximum concentration (10.5% wt). At this maximum concentration there was no evidence of particle settling.

As the Yield Stress of the MR fluid can be modified according to the intensity and direction of the magnetic field, two different approaches are evaluated to estimate the pressure drop in concentric annuli for laminar flow as a function of the Yield Stress (as described in Ermila, M., Eustes, A. W., & Mokhtari, M. (2012). Using magneto-rheological fluids to improve mud displacement efficiency in eccentric annuli. SPE Eastern Regional Meeting, 17-29. Retrieved from http://www.scopus.com/inward/record.url?eid=2-s2.0-84873803403&partnerID=tZOtx3y1 and Kelessidis, V. C., Dalamarinis, P., & Maglione, R. (2011). Experimental study and predictions of pressure losses of fluids modeled as Herschel-Bulkley in concentric and eccentric annuli in laminar, transitional and turbulent flows. Journal of Petroleum Science and Engineering, 77(3-4), 305-312. https://doi.org/10.1016/j.petrol.2011.04.004). These approaches are derived from the Navier-Stokes equations for incompressible fluids. Also, an empirical equation is used to determine the yield stress as a function of the magnetic field applied to the MR fluid. For the pressure drop calculations, the following approaches are presented and are compared to the results obtained experimentally:

The Ermila et al model was obtained to estimate the frictional losses for laminar regimes for Herschel-Bulkley fluids in concentric annuli:

$\begin{matrix} {q = {\left\lbrack \frac{{\pi \left( {r_{2}^{2} - r_{1}^{2}} \right)}\left( {r_{2} - r_{1}} \right)^{1 + m}\left( \frac{1{dp}}{KdL} \right)^{m}}{2^{m}\left( {m + 1} \right)\left( {{2m} + 4} \right)} \right\rbrack \cdot {\quad{\left\lbrack {1 - \frac{\tau_{y}}{\left( \frac{r_{2} - r_{1}}{2} \right)\left( \frac{dp}{dL} \right)}} \right\rbrack \cdot \left\lbrack \frac{\frac{\tau_{y}}{r_{2} - {r_{1}\left( \frac{dp}{dL} \right)}} + m + 1}{2^{m}\left( {m + 1} \right)\left( {{2m} + 4} \right)} \right\rbrack}}}} & (1) \\ {\mspace{79mu} {m = {1/n}}} & (2) \end{matrix}$

Where, r₂ is the outer radius and r₁ is the inner radius [m], q is the flow rate [m³/s], δp/δL is the pressure drop gradient [Pa/m], τ_(y) is the field dependent yield stress [Pa] and n is the flow behavior index.

The Kelessidis et al model is applicable for laminar, transitional and turbulent regimes and uses the same correlations for laminar flow as per API Recommended Practice 13D. Also, estimates the pressure losses for a Herschel-Bulkey in 100% concentric annulus, other expressions for eccentric annuli are presented in the publication. The model is simplified to the following expression for transition and turbulent regimes:

$\begin{matrix} {\frac{\Delta \; p}{\Delta \; L} = \frac{2f\; \rho \; V^{2}}{d_{o} - d_{i}}} & (3) \end{matrix}$

Where, Δp/ΔL is the pressure drop gradient [Pa/m], f is the Fanning friction factor, ρ is the fluid density [kg/m³], V is the mean velocity [m/s], d_(o) is the diameter of the outer tube of annulus, and d_(i) the diameter of inner tube of annulus [m].

$\begin{matrix} {V = \frac{4 \cdot q}{\pi \left( {d_{o}^{2} - d_{i}^{2}} \right)}} & (4) \end{matrix}$

Where, q is the flow rate.

The flow regime is a function of the channel shape and size, fluid viscosity and fluid density. For the maximum flow rate and the type of fluid used during the experimental phase, the flow regime experienced is laminar. For the laminar flow portion, the Fanning friction factor (f) is well represented by the following expression:

$\begin{matrix} {f = \frac{24}{Re}} & (5) \end{matrix}$

Where, Re represents the Reynolds number.

$\begin{matrix} {{Re} = \frac{\rho \; {V^{({2 - n^{\prime}})}\left( {d_{o} - d_{i}} \right)}^{n^{\prime}}}{{K^{\prime}(12)}^{n^{\prime} - 1}}} & (6) \end{matrix}$

Where, n′ is the flow behavior index for local power-law parameters and K′ is the flow consistency index for local power-law parameters.

$\begin{matrix} {n^{\prime} = \frac{{n\left( {1 - ɛ} \right)}\left( {{n\; ɛ} + n + 1} \right)}{1 + n + {2n\; ɛ} + {2n^{2}ɛ^{2}}}} & (7) \end{matrix}$

Where, n is the flow behavior index from equation (10) and ε is the dimensionless shear stress for annulus from equation (12).

$\begin{matrix} {K^{\prime} = \frac{\tau_{y} + {K\left( {\frac{{2n^{\prime}} + 1}{3n^{\prime}}\gamma_{Nw}} \right)}^{n}}{\left( \gamma_{Nw} \right)^{n^{\prime}}}} & (8) \end{matrix}$

Where, τ_(y) is the field dependent yield stress [Pa], γ_(Nw) is the Newtonian shear rate on the wall [s⁻¹] and K is the flow consistency index.

$\begin{matrix} {K = \frac{510 \cdot \theta_{300}}{511^{n}}} & (9) \end{matrix}$

Where θ_(x00) is the the cylindrical viscosimeter reading at the corresponding shear rate.

$\begin{matrix} {n = {3.32\mspace{14mu} \log \frac{\theta_{600}}{\theta_{300}}}} & (10) \\ {\gamma_{Nw} = \frac{12V}{d_{o} - d_{i}}} & (11) \end{matrix}$

V is the mean velocity [m/s] from equation (4).

$\begin{matrix} {ɛ = \frac{\tau_{y}}{\tau_{w}}} & (12) \end{matrix}$

Where, τ_(w) is the shear stress at the wall [Pa].

The yield stress can be modeled as well. The model proposed by Carlson and presented by Goncalves (in Goncalves, F., Guth, D., & Maas, J. (2015). Characterization and modeling of the behavior of magnetorheological fluids at high shear rates in rotational systems. Journal of Intelligent Material Systems and Structures, (January), 114. https://doi.org/10.1177/1045389X15577646) relates the yield stress τ_(y) and the magnetic field strength H:

τ_(y) =C·271700·Ø^(1.5239)·tan h(6.33·H)   (14)

Where, τ_(y) is the field dependent yield stress [Pa], H is the magnetic field strength in [A/m], Ø is the magnetizable particle concentration as a fraction and C is a constant that depends on the carrier fluid given as:

C=0.95 Silicone Oil C=1.0 Hydrocarbon Oil C=1.16 Water

Various results were obtained from the experimental setup. The fluid was circulated in the experimental setup at the minimum concentration of CIP (0.447 wt %), the pressure drop was measured and recorded. The CIP concentration was increased incrementally until reaching the maximum concentration (10.5% wt). The annulus pressure drop between transducers P4-P5, where the magnet arrangement is located, was recorded and compared to the models. In these models, Ermila and Kelessidis, the field dependent yield stress was calculated using the Equation (14) from the magnetic fields presented in Table 1—Magnetic Field [mTesla]. Table 3 (below) and FIG. 29 summarizes the pressure drop measurements and the simulated at a flow rate of 21.1 gpm at different concentrations. FIG. 29 shows a pressure drop comparison of the models and measured data for MRF CIP wt % 10.5.

TABLE 3 Pressure Drop Determination at 21.1 gpm Expected Pressure drop Pressure Simulated Carbonyl Iron without Drop Ermila et Particles the Transducers al Simulated Concentration Magnets P4-P3 [psi] Approach Kelessidis [wt %] [psi] at 21.1 gpm [psi] et al [psi] 0.447 0.4996 0.5103 0.1380 0.1705 0.894 0.4996 0.664 0.1612 0.1869 1.341 0.4996 1.031 0.1915 0.2083 1.788 0.4996 1.222 0.2278 0.2339 3.576 0.4996 1.345 0.4192 0.3690 4.917 0.4996 1.3536 0.6026 0.4984 5.588 0.4996 1.3647 0.7052 0.5708 6.258 0.4996 1.4363 0.8145 0.6479 6.929 0.4996 1.5698 0.9300 0.7294 7.599 0.4996 1.6352 1.0516 0.8152 8.270 0.4996 1.3118 1.1790 0.9051 8.941 0.4996 1.1033 1.3119 0.9988 9.611 0.4996 1.4151 1.4501 1.0963 10.505 0.4996 1.333 1.6423 1.2320

The calculations determined that an additional pressure drop can be generated across the magnets as a function of the magnetic field strength and the concentration of the CIP. Additionally, the pressure drop measurements show a steady increase until a CIP concentration of 7.599% wt. This is interpreted as a maximum saturation where the magnetizable particles are affected by the magnetic field strength. The simulated pressure drop values are higher in Ermila et al model because it gives a higher pressure drop effect to the value of the field dependent yield stress in comparison to Kelessidis et al.

The MRF with a CIP concentration of wt % 10.5 was held static for a period of 60 hours inside the experimental setup to evaluate its behavior. When the fluid was circulated after this period, the pressure drop across the magnets showed an increased in comparison to the measurements previously presented i.e. at 21.1 gpm the pressure drop across the magnets was 1.33 psi whereas the new measurement rounded 3.11 psi, as shown in FIG. 30. FIG. 30 shows a pressure drop measurement at different flow rates MRF CIP wt % 10.5 after 60 hours static.

The preliminary interpretation of the results is that the rheology of the MRF can be modified accordingly to the magnetic field strength and magnetizable concentration. However, for the parameters of this particular experimental set-up, it does not play the dominant role in the packing and/or pressure drop. Instead, the built-up iron particles create a mechanical restriction as shown in FIG. 31. FIG. 31 shows a pressure drop measurement drip-pipe & annulus with MRF CIP wt % 10.5 after 60 hours static.

Although the benefits of applying the MRF are clear and known for scientists and industries that have used this type of fluids, this technology needs more research to overcome its inherent challenges. As an example, one of the most relevant problems is the MRF instability against sedimentation and low MR effect (as described in Ashtiani, M., Hashemabadi, S. H., & Ghaffari, A. (2015). A review on the magnetorheological fluid preparation and stabilization. Journal of Magnetism and Magnetic Materials, 374, 711-715. https://doi.org/10. 1016/j.jmmm.2014.09.020). The magnetic particles have a high specific gravity, or weight, making it difficult for the carrier fluid to keep them dispersed homogeneously in the fluid. Several stabilization methods have been studied such as: Particle coating, Nano spherical Particles, various carrier fluids, other additives as surfactant and thixotropic agents, and Nano Wire Particles (Ashtiani, Hashemabadi, & Ghaffari, 2015). The MRF can find application in high temperature and high-pressure environments, proper for the Oil and Gas Industry.

The Oil and Gas Industry has relied its drilling operation to conventional (conventional, in the sense of being not active in the presence of a magnetic field) drilling fluids that have some limitations. However, potential application of using Magnetorheological Fluids to create fluid barriers downhole could be explored. Therefore, if a magnetic field strength is generated downhole, the pressure drop of the MRF could be high enough to block the flow. This property has the potential to reduce fluid losses and gas migration.

A magnetic field responsive fluid was developed with the incorporation of Carbonyl Iron Powder (CIP), a magnetizable particle, on a water-bentonite dispersion. It has been shown that increasing the concentration of the CIP in the presence of a magnetic field is responsible for the modification of the rheological properties of the fluid. In that sense, a non-chemical rheology modification was presented experimentally. Particularly, the rheology effect can be predicted by determining the magnetic field dependent yield stress and the concentration of the magnetizable particles. The pressure drop on a laminar flow regime in a concentric annulus could be modeled considering the Herschel-Bulkley Model.

Additionally, a packing effect could be observed after the MRF sample remained static for a period of 60 hours. The preliminary interpretation is that this effect could be created through the built-up of the magnetizable particles in front of a magnetic field. We expect that, depending on the magnetic geometry and strength and also the recipe design of the MR fluid, the magneto-rheological effect versus the physical blockage as a result of magnetic particles built-up around the magnet will compare differently.

In the case of these experiments, the pressure drop effect can be increased as a function of the time exposure to the magnetic field and to a less extent, to the instantaneous rheology modification when the MRF crosses in front of the magnetic field. The ability of the MRF to create a pressure drop and potentially a fluid barrier, can be used in the future for potential applications such as controlling fluid losses or temporarily zonal isolation.

Any of the examples described herein may include MRF that includes “proppants” that are widely used in hydraulic fracturing operations. Additionally, any of the examples described herein may be implemented and a conductivity log run to determine the fracture (or injection) shape, distribution, etc. from the spikes in the measured conductivity and using the values of MRF resistivity as weight averaged from their recipe.

Any of the examples described here may include a work-string, or a plurality of work strings, with a magnetic assembly installed on the work-string(s). The work-string can for example be pulled out of the hole with a speed slow enough allowing several stages of hydraulic fracturing.

Also, any of the described examples can include an application of a magnetic field to the MRF over a period of time. Experimental results have shown that if a magnetic field is applied to MRF that remains static for 60 hours, there is a build-up of magnetorheological particles near the magnetic field that is capable to create a mechanical barrier. In other words, in some examples a restriction caused by the built-up iron particles creates a mechanical restriction that plays a dominant role in the packing and/or pressure drop. The fluid rheology could still be modified in these examples.

The term “substantially” is meant to permit deviations from the descriptive term that don't negatively impact the intended purpose. Descriptive terms are implicitly understood to be modified by the word substantially, even if the term is not explicitly modified by the word substantially.

It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt % to about 5 wt %, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. The term “about” can include traditional rounding according to significant figures of numerical values. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to about ‘y’”.

A related description of certain magnetic gradient drilling concepts that may be relevant to the disclosure provided herein, including descriptions of a magnetic assembly tool that includes a magnetic shielding material to shield at least part of the magnetic field, is provided in PCT Publication No. WO 2017173305, titled “MAGNETIC GRADIENT DRILLING,” filed on Mar. 31, 2017, and which is herein incorporated by reference in its entirety.

It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

NOMENCLATURE

-   d_(i) diameter of inner tube of annulus (m) -   d_(o) diameter of outer tube of annulus (m) -   δP/δL pressure drop gradient (Pa/m) -   f Fanning friction factor -   H magnetic field strength (kA/m) -   K flow consistency index (Pa·s^(n)) -   L length (m) -   m power exponent -   n flow behavior index -   n′ flow behavior index for local power-law parameters -   Q flow rate (gal/min) -   q flow rate (m³/s) -   r_(i) radius (m) -   Re Reynolds number -   V mean velocity (m/s) -   γ shear rate (s⁻¹) -   γ_(Nw) Newtonian shear rate on the wall (s⁻¹) -   γ_(w) wall shear rate (s⁻¹) -   ε dimensionless shear stress for annulus -   ρ fluid density (kg/m³) -   τ shear stress (Pa) -   τ_(y) field dependent yield stress (Pa) -   τ_(w) wall shear stress (Pa) -   BHA bottomhole assembly -   PPG pounds per gallon -   Cp centipoise -   SEM scanning electron microscope -   Lbs. pounds -   Bbl. barrel -   EDS electron dispersive spectrometer -   Ft. feet -   S second -   DAQ data acquisition 

At least the following is claimed:
 1. A system, comprising: a magnetic assembly tool; a magnetorheological fluid comprising magnetorheological particles; and placing the magnetic assembly tool to apply a magnetic field to a flow of the magnetorheological fluid to create at least one of: a semi-solid packing element based on a build-up of the magnetorheological particles near the magnetic field, or a magneto-rheological effect based on an alignment of the magnetorheological particles with the magnetic field.
 2. The system of claim 1, wherein placing the magnetic assembly tool further comprises to achieve a purpose of at least one of: to release a differential sticking, to form a seal in a sub-pressurized formation, to allow several stages of hydraulic fracturing, to create a selective-resettable zonal packer, to isolate at least one of gas or water, or to set at a designated depth in a plug and abandonment operation.
 3. The system of claim 1, wherein placing the magnetic assembly tool comprises placing the magnetic assembly tool in a drill pipe to release a differential sticking.
 4. The system of claim 1, wherein placing the magnetic assembly tool comprises embedding the magnetic assembly tool outside a drill pipe.
 5. The system of claim 1, wherein the magnetic assembly tool comprises an arrangement of a plurality of magnets, and the placing the magnetic assembly tool comprises embedding the arrangement inside a casing.
 6. The system of claim 1, wherein the at least one of: the semi-solid packing element based on the build-up of the magnetorheological particles near the magnetic field, or the magneto-rheological effect based on the alignment of the magnetorheological particles with the magnetic field is in a plurality of annuli.
 7. The system of claim 1 wherein the at least one of: the semi-solid packing element based on the build-up of the magnetorheological particles near the magnetic field, or the magneto-rheological effect based on the alignment of the magnetorheological particles with the magnetic field is between a pipe and an annulus.
 8. The system of claim 7, comprising the build-up of the magnetorheological particles between the pipe and the annulus.
 9. A magnetorheological fluid, comprising: a suspension of magnetic particles in a liquid, wherein: the liquid comprises a drilling fluid; and the magnetic particles comprise an iron powder.
 10. The magnetorheological fluid of claim 9, wherein the iron powder is at least one of: a soft grade Carbonyl Iron Powder (CIP), or a hard grade CIP.
 11. The magnetorheological fluid of claim 9, further comprising at least one of: a viscocifier agent, or a carrier fluid.
 12. The magnetorheological fluid of claim 11, wherein the viscocifier agent is at least one of synthetic colloidal clay Laponite RD, non-polar Polyalphaolefin (PAO), Dioctyl Sebacate (DOS), Carbonyl Methyl Cellulose (CMC), or Xanthan Gum Kelzan.
 13. The magnetorheological fluid of claim 11, wherein the carrier fluid is at least one of: a petroleum-based oil, a mineral oil, water, a paraffin oil, a silicon oil, a polyether, a glycol, or a cement slurry.
 14. A magnetic assembly tool, comprising: an arrangement of at least one of a plurality of magnets configured to alter at least one of a plurality of rheological properties of at least one region of a flow of a magnetorheological fluid, the arrangement comprising at least one of a ring, a segmented ring, a multi-segmented ring, or a spiral; and the arrangement further comprising an orientation of the at least one of the plurality of magnets configured to create at least one of: a build-up of magnetorheological particles of the magnetorheological fluid, or a magneto-rheological effect based on an alignment of the magnetorheological particles with a magnetic field.
 15. The magnetic assembly tool of claim 14, wherein the arrangement is configured to be placed in at least one of: a drill pipe, a casing, or a hole.
 16. The magnetic assembly tool of claim 14, wherein the arrangement is the ring and the orientation comprises a dipole of each one of the at least one of the plurality of magnets oriented in a same radial direction.
 17. The magnetic assembly tool of claim 14, wherein the at least one of the plurality of magnets comprises at least one of: a permanent magnet, an electromagnet, or a magneto-elastic magnet.
 18. The magnetic assembly tool of claim 14, wherein the arrangement is located on at least one of: a tubing, a wireline, or a bottom-hole assembly (BHA).
 19. The magnetic assembly tool of claim 14, further comprising an attachment configured to locate the at least one of the plurality of magnets on a downhole tool.
 20. The magnetic assembly tool of claim 14, wherein the at least one of the build-up of magnetorheological particles or the magneto-rheological effect generates a packing mechanism comprising at least one of: a radial packing or a lateral packing. 